Apparatus for coating articles at high temperature



1956 G. H. BURNETT ET AL 2,764,956

MPERATURE APPARATUS FOR C OATING ARTICLES AT HIGH Filed Jan. 26, 1955 2 Sheets-Sheet l /5 Invervlrovs: 2/ Ge'or'ge HBUYTWe t t,

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1956 G. H. BURNETT TAL APPARATUS FOR COATING ARTICLES AT HIGH TEMPERATURE 2 Sheets-Sheet 2 Filed Jan. 26, 1955 Invervtors: Geow ge- H. Buvnefir t', Vic tow" LFinizio, b5

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Unite States Patent APPARATUS FOR CGATIN G ARTICLES AT HIGH TEMPERATURE George H. Burnett, Cleveland Heights, and Victor L. Finizio, South Euclid, Ohio, assignors to General Eleotric Company, a corporation of New York Application January 26, 1955, Serial No. 484,194 7 Claims. (Cl. 118-41) The present invention relates to coating apparatus and its principal object is to provide such an apparatus useful in the arts generally and particularly for applying a thin, electroconductive, transparent film to the outer surface of tubular glass discharge envelopes for flashtubes useful in photography.

Flashtubes for photography are provided with trigger electrodes which effect the flashing of the tube. The trigger electrode is external to the glass envelope of the flashtube and may be in the form of a metal wire wrapped around the envelope or an adherent electro-conductive, transparent film on the outer surface of the envelope. The film is preferred commercially because of the better appearance of fiashtubes provided therewith, among other reasons.

In the mass production of such flashtubes, an apparatus for quickly and effectively applying an adherent film of this kind to the external surface of the tubular glass discharge envelopes of a plurality of flashtubes is essential. The apparatus described below has proven eminently satisfactory for the purpose.

The apparatus embodying the invention comprises four main units in combination which may be mounted on a stationary table of standard height for convenience. The units include a shallow circular oven open at the bottom and mounted in an elevated horizontal position on the table and having continuously operating radianttype heaters set radially into its interior circular side Wall, an envelope support mechanism including a turntable adapted to support a pallet of lamp envelopes slid bodily thereon and means for lifting the turntable from a position level with the surface of the table up to the oven to close the bottom opening thereof and for returning the turntable to its original position at the level of stationary table for bodily removal of the pallet from the apparatus after the supported glass envelopes have been coated in the oven; a spray mechanism including a spray nozzle and means to move the nozzle in a horizontal direction into a side port of the oven from a position outside the oven and to retract the nozzle from the port, and means for controlling the functioning of the envelope support mechanism and the spray mechanism in properly timed sequence to elfect coating of the glass envelopes.

In the accompanying drawing:

Fig. l is a vertical section of the new coating apparatus, the view being taken along the line 1, 1 of Fig. 2 in the direction of the arrows and showing hydraulic and electrical controls of the apparatus partly in full and partly diagrammatically;

Fig. 2 is a plan view of the apparatus with approximately one-half of the oven and adjacent means broken therefrom in order to show the position of the spray nozzle or gun in relation to the coating position of the discharge lamp envelopes in the oven of the apparatus;

Fig. 3 is a perspective view of doors mounted opposite a spray gun outer opening or port of the oven and of the means for operating the doors.

Like numbers denote like parts in all the figures.

The apparatus illustrated in Figs. 1-2 is shown part way through its cycle of operation with the parts thereof slightly displaced for clarity of illustration from the positions occupied thereby during spraying of the lamp envelopes.

The apparatus comprises a stationary table 1, at which an operator may be seated, and an oven 2 mounted above the table on three spaced apart legs 1, only two of which are shown. The lamp envelopes 3 and 4 of borosilioate glass, for example, to be coated by the apparatus are arranged by the operator in spaced nested relation upon the upper surface of an individual tray or pallet 5 before the pallet is inserted in the coating apparatus. The envelopes 3 and 4 are of bent configuration, the envelopes 4 having a single helical turn at the center portion thereof and the envelopes 3 being of U shape. The two end portions of each of the envelopes 3 and 4 are coplanar and parallel.

The arrangement of the envelopes 3 and 4 on the pallet 5 is done manually by the operator in such manner that the ends thereof rest in shallow pockets in the upper of the two generally circular platforms 6 and 7 making up the pallet 5'. The exhaust tubes 8 of the U shaped envelopes 3 rest against the upper platform 6 and the corresponding tubes 8 of the convoluted envelopes 4 extend vertically upward.

Both shapes of lamp envelopes are shown in the drawing though it will be understood that usually all the envelopes coated at one time will be of the same shape for convenience in handling and loading.

The loading of one pallet 5 may be performed by the operator while the envelopes on another pallet are being coated automatically by the apparatus, and this preloading of the pallet is usually completed by the time the apparatus has completed its cycle of operation and the turntable 9 has returned to its original position within the opening 10 of the table. At such time, the pallet 5 on the turntable 9 is removed bodily from the apparatus and replaced by a preloaded pallet.

The pallets 5, which are preferably made of heat resistant asbestos board, slide freely across the surface of the table 1. The center portion of the lower surface of the platform 7 of the pallets is cupped slightly so as to fit and frictionally engage the raised locating crown 11 of the turntable 9.

, Once a preloaded pallet Sis centralized on the turntable 9 by fitting the bottom platform 7 thereof on the raised crown 11, the automatic cycle of operation of the apparatus is initiated by the operator by tripping the control switch 12 to set in motion the timer 13 which is the master control for all portions of the apparatus.

All succeeding operations of the apparatus are either directly or indirectly dependent upon the operations of the timer 13 as described hereinafter. The timer can be any one of several commercial timers adapted for the sequence and interval control of the connections of a group of electrical circuits, in the present instance, the connections between individual electrical circuits of the apparatus and the terminals 14 of a current supply source.

The immediate function of the timer 13 upon being placed in operation by closing switch 12 is to energize the actuating means of the turntable 9 to movethelatter upwa'id from the level of the table 1 to' a position within the openingZ' iii the bottonl of the oven 2 so as to position the pallet 5 and the envelopes 3 and 4 thereon in proper position for coating the envelopes within the heat chamber of the oven. v

To effect this operation, the timer l3 energizes the solenoid valve 15 by connecting the leads 16 and 17 there} for across the power terminals 14 to cause the valve 15 to admit compressed air into the lower end of the vertical air cylinder 18 located at the lower end of the support spindle 19 of the turntable 9 (Fig. 1) and thereby raise the support spindle 19 and therewith the turntable 9. The compressed air system for the cylinder 18 includes the pipe 20 connected to a source (not shown) of compressed air and a pipe 21 connected to the control valve 15 and the lower end of the cylinder 18. Another pipe 22 is connected to the upper end of the cylinder 18 and to the valve 15 and vents said upper cylinder end through the valve 15 when the piston 23 in the cylinder 18 is moved upward by the compressed air entering the lower end of the cylinder 18.

The support spindle 19 is connected at its lower end to the piston 23 of the hydraulic jack 18, 23 by a coupling 24, so that the piston 23, the spindle 19 and the turntable 9 move up and down together.

The spindle 19 is guided in its vertical movements by the spaced vertically aligned bearing blocks 25 and 26. The block 25 engages the cylindrical lower section of the spindle 19 and the block 26, through an intermediate sleeve 27, engages the splined upper portion 28 of the spindle 19. A frame 29 bolted to the table 1 and made up of securely fastened together members provides the support for the cylinder 18 and the bearing blocks 25 and 26.

When the turntable 9 has been moved to its fully lifted position by the mechanism described above, the lamp envelopes 3 and 4 are subjected immediately to the full radiant heat from a series of continuously operating gas burners 30 located in the circular wall 31 of the oven 2 and forming substantially the entire side wall of the chamber defined by the oven 2. Each of the burners 30 is coupled by a branch pipe 32 to a gas and air manifold 33 encircling the oven 2 and burns the gaseous combustible mixture completely within the end cavity of the refractory body 35 (Fig. 2) comprising the main element thereof. The flame is generated in the cavity 34 at a position about the center button 36 of the burner.

The continuously operating burners 30 are of such capacity as to maintain the walls 31 and top 37 of the oven 2 at nearly full operating temperature even during the period when the turntable 9 is at the level of table 1 and a relatively heavy current of air passes through the open bottom of the oven 2 to the flue 38. The relatively high heat capacity and the radiant manner of heating is responsible for a very rapid transfer of heat to the lamp envelopes 3 and 4 to quickly raise the envelopes to the proper temperature for coating.

In order for all lamp envelopes 3 and 3 upon the pallet to be heated uniformly in the oven 2, means are provided for slowly rotating the turntable 9 while in its lifted position, so that each of the envelopes 3 and 4 is exposed as equally as possible to the burner radiation. The rotative movement of the turntable 9 takes place when it is fully lifted with the envelopes 3 and 4 in coating position in the oven 2. At this time the timer 13 energizes an electric motor 40 by connecting the leads 41 and 42 across the terminals 14. The motor 40 is mechanically connected to the spindle 19 of the turntable 9 through the reduction gearing in housing 43, a sprocket 44 on shaft 45 of the reduction gearing in housing 43, the chain 46 and a second sprocket 47 journaled upon a portion of the sleeve 27. A dog 48 clamped to the spindle 19 and engaging the sprocket 47 through a stud 49 projecting into one of a series of openings around the sprocket 47 com pletes the turntable rotating means and functions as a clutch which automatically disengages the rotating means from the spindle 19 when the spindle and the turntable 9 are lowered from the lifted position shown in Fig. 1. In one particular cycle of operation suited to the formation on the outer surface of the envelopes 3 and 4 of an adherent, electrically conductive, transparent film from a spray solution including one part indium chloride and from one to three parts water, inclusive, it is desirable that the envelopes 3 and 4 be preheated or baked for a period from at least about 30 seconds to not more than about five minutes while the oven 2 is maintained at a temperature of about 600 C.

At the end of the heating period, an opening or port 50 at the level of the heaters 30 in the side wall 31 of the oven 2 is exposed by the separation of metal doors 51 and 52 (Figs. 2 and 3) and the spray gun 53 (Figs. 1 and 2) is caused to advance from a retracted position completely outside the oven 2 to a spraying position within the opening 50. In Figs. 1 and 2 the gun 53 is shown in an advanced position.

Both operations, that is, the opening of the doors 51 and 52 and the movement of the spray gun 53, are initiated by the timer 13 which connects the leads 54 and 55 extending from the solenoid valve 56 to the current supely terminals 14, thus energizing the solenoid valve which admits compressed air into the air cylinder 57 associated with the mounting for the spray gun 53 and associated also with the operating mechanism of the doors 51 and 52, as described below.

The compressed air passes from the supply pipe 58 connected to a compressed air source (not shown) to the pipe 59 connected with one end of the cylinder 57. The opposite end of the cylinder 57 is vented through the pipe 60 and the valve 56.

The piston 61 at this latter end of the cylinder 57 is connected by the pin 62 to the lower end of the forward support lever 63 for the spray gun 53 and moves the spray gun 53 by turning the lever 63 about the pin 64.

The position of the spray gun 53 is essentially a horizontal one as it is advanced into the opening 59, because it is supported by a carriage 65 pivoted at 66 upon the lever 63 and at 67 upon the arm 68. Movement of lever 63 causes the lever 63 and the arm 68 to turn about the pins 64 and 69, respectively, in the mounting brackets 70 and 71, respectively, attached to the table 1. The spray gun 53, except when spraying, is positioned with the head end or nozzle 72 thereof outside the oven and spaced slightly from the oven doors 51 and 52. The doors 51 and 52 are then in a closed position to protect the gun 53 from the heat of the oven 2. In the course of the first part of the advance movement of the spray gun the oven doors 51 and 52 are opened to allow the head 72 to pass directly into the opening 50 of the oven 2.

The movement of the oven doors 51 and 52, which are shown in detail in Fig. 3, is effected by the first part of the rotation of the lever 63 about the pin 64. The movement of lever 63 advances the roller 73 mounted on a lateral extension 74 of the lever 63 between the closely spaced lower ends of the doors 51 and 52. The roller 73 wedges the lower ends of the doors 51 and 52 apart and by so doing causes them to turn about the supporting pivot pins 75, 75 extending from the bracket 76 in opposition to the contraction force of the helical spring 77 which tends to move the doors 51 and 52 to a closed position.

The spray gun 53 is advanced fully into the port 50 before it is made operative. With the gun 53 in such advanced position, compressed air is admitted to the upper tube 80 thereof and, by way of an example, the above-mentioned aqueous solution of indium chloride is valved to the lower tube 81 thereof. The spray ejected by the head 72 sweeps across the turntable 9 and deposits upon the envelopes 3 or 4 in its path. The position of the spray gun 53 is such that the spray reaches the envelopes 3 and 4 from a point slightly above the envelopes and accordingly covers all of the top portion of the envelopes. The rotation of the turntable 9 and the nested arrangement of the envelopes 3 and 4 contributes to the distribution of the spray uniformly on all outer surfaces of the envelopes 3 and 4. The envelopes are usually completely spray coated within a 15 second interval and one complete revolution of the turntable 9.

The spray gun 53 is a relatively simple aspirator type made of glass with a straight through tube 81 connected to the coating solution, and with a tubular head end 72 surrounding the open end of tube 81 and connected to the air supply tube 80. The tubes 80 and 81 also .provide the support for the spray gun 53 in that they are clamped to the carriage 65 by a screw-attached plate 83 on one side thereof.

The length of the spray period is controlled, as diagrammatically illustrated in Fig. l, by the timer 13 and by the support means for the spray gun 53, respectively.

The timer 13 controls the air supply to the gun 53 through the current carrying leads 84 and 85 connected to the solenoid valve 86. The latter is coupled to the compressed air supply pipe 87 and to the pipe 80 of the gun 53 through piping 88, part of which consists of a flexible hose to allow the gun -3 to move without break ing the air connection.

Control of the spray solution supply for the gun 53 is eflected through the lever 63 of the spray gun support means in the following manner: The rod 89 is loosely connected to the lever 63 and is also connected to a movable arm 90 which, in all positions other than the furthermost advanced position of the lever 63, squeezes a section of the rubber hose 91 leading to the tube 81 against the bracket 71 to close the hose 91. Until the spray gun 53 is advanced to its opera-ting position the spray of coating solution through the rubber hose 91 is prevented by the pressure of a helical spring 92 against the arm 91 which is pivoted upon a pin 93 retained by the bracket 71. These elements constitute a pinch clamp for the rubber hose 91.

it is not until the lever 63 engages the nuts 94 at the end of the rod 89 as it advances the gun 51 into the port 50 that said rod 89 pulls the arm 90 away from the bracket '71 against the force of the spring 92. When this takes place the hose 91 can expand to its normal shape to allow the coating solution to flow through to the head 72 of the spray gun.

It has been found that two relatively short spray periods produce a better coating than one such period of longer duration. Thus, the timer 13 is set to effect retraction of the spray gun 53 from the port 50 at the end of a spray period of 15 seconds and then, after a lapse of 30 seconds, to again effect advancement of the gun 53 into the oven port 50 for another 15 second spray period.

Retraction of the spray gun 5-3 from the oven port is effected by timer 13 which actuates the valve 56 in such manner as to connect the compressed air pipe 58 with the pipe 50 and to open the end of pipe 54 so as to vent the end of air cylinder 57 to which pipe 59 is connected.

The 30 second time lapse between the two spraying operations allows the oven to compensate for the heat lost by the envelopes 3 and 4 during the first spray period. The temperature of the envelopes 3 and 4 is thus maintained within narrower limits during the entire coating operation than is possible with a single spray period of longer duration and better coatings are produced on the envelopes.

After the spray gun 53 is withdrawn the second time, the envelopes 3 and 4 are retained in the oven for approximately 30 seconds. During this time the conversion of the sprayed coating on the envelopes 3 and 4 to an adherent, electrically conductive, transparent film is completed.

At the end of the 30 second period, the envelopes 3 and 4 are removed from the oven 2 by lowering the turntable to the level of the table 1. The pallet 5 on which the coated envelopes rest is removed bodily from the apparatus and another pallet preloaded with uncoated envelopes 3 and 4 is placed on the turntable 9, as previously described.

The lowering of the turntable 9 after the last 30 second period is eifected by the timer 13 which actuates the valve 15 in a manner to cause the compressed air pipe 20 to admit air into the upper end of the cylinder 18 through the pipe 22 and to vent the lower end of the cylinder 18 6 to the atmosphere through pipe 21. This completes the operating cycle of the apparatus.

After the pallet 5 of coated envelopes has been slid off the turntable 9 onto the table 1, a preloaded pallet of envelopes to be coated is slid on the turntable 9 and the control switch 12 is again tripped by the operator to set in motion the timer 13 and therewith the coating apparatus.

While the preferred embodiment of the invention has been shown and described, it will be understood that the invention is not limited to this exact structure and it will be understood that many modifications of the precise manner by which the invention is carried into effect may be made without departing from the scope of the appended claims; tor example, the timer 13 may be set to provide a sequence of operations and time intervals for the various operations of the elements of the combination different from those given above to adapt the apparatus for coating articles of diiferent materials and shapes and for use with spray materials of different composition, such as solutions of tin salts, to provide coatings of similar or different characteristics on the articles.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A spray coating apparatus comprising in combination, a stationary support, an oven mounted above said support, the walls of said oven defining a spray chamber and a bottom opening and a port into said chamber, an article suport mechanism mounted on said stationary support and including means for moving supported articles between a loading position below said oven and a spraying position within said oven, said article support mechanism being adapted to close said oven opening, a spray mechanism mounted on said support outside said oven and including a nozzle movable into and out of said port and means for moving said nozzle into and out of said port from a position outside said oven, and timing means for said article support mechanism and said spray mechanism to eifect spray coating of hot articles in said oven chamber.

2. A spray coating apparatus comprising in combination, a horizontal support, an oven mounted in an elevated position on said support, the walls of said oven defining a circular spray chamber and a bottom opening and a side port into said chamber and having a plurality of heaters radially mounted in the circular side wall of said chamber at about the level of said port, article support means mounted for vertical movement on said horizontal support between a loading position at the level of said horizontal support and a position Within said opening for supporting Within said chamber articles to be coated, spray means mounted on said support and movable thereon into and out of said port, individual actuating means for said article support means and said spray means and timing means for said individual actuating means to effect spray coating of hot articles in said chamber.

3. A spray coating apparatus comprising in combination, ahorizontal support, an oven mounted in an elevated position on said support, the walls of said oven defining a spray chamber and a bottom circular opening into said chamber, heating means in said oven and disposed around the space above said opening, an article support mechanism comprising a turntable movable on said support from the level of the horizontal support to the level of the bottom opening of said oven and being adapted to close said opening, means to lift said turntable from a loading position at the level of said support to the level of the said opening and to lower said turntable to its original position, means to rotate said turntable and means to connect said turntable with said rotating means on lifting of said turntable and to disconnect said turntable from said rotating means on lowering of said turntable, said apparatus comprising also means for spraying articles supported by said turntable in said chamber and timing 7 means for said support mechanism and said spray means to effect spray coating of hot articles in said chamber.

4. A spray coating apparatus comprising in combination, a horizontal support, an oven mounted in an elevated position on said support, the walls of said oven defining a spray chamber and a bottom opening for the reception of articles within said chamber and having also a side port into said chamber, an article support mechanism including means movable on said support from a loading position at the level of said support to a position within said opening, spray means mounted opposite said port for horizontal movement on said support and actuating means on said support for moving said spray means into said port for spraying articles in said chamber and for retracting said spray means completely from said port after spraying and timing means for said article support mechanism and said spray actuating means to effect spray coating of hot articles in said chamber.

5. A spray coating apparatus comprising in combination, a stationary support, an oven mounted on said support, the walls of said oven defining a spray chamber and an opening for the reception of articles in said chamber and a side port into said chamber, an article support mechanism including means movable on said support from a loading position outside said oven to a position within said opening to close said opening, spray means mounted on said support opposite said port and actuating means to move said spray means into said port and to retract said spray means from said port, said apparatus comprising also closure means for said port and means for moving said port closure means from a closed to an open position, and means connecting the actuating means for said spray means and the actuating means for said closure means whereby said closure means is moved from a closed position to an open position on advancement of said spray means into said port and is returned to a closed position on retraction of said spray means from said port and timing means for said article support mechanism and said spray actuating means to effect spray coating of hot articles in said chamber.

6. A spray coating apparatus comprising in combination, a horizontal support, a shallow oven mounted in an elevated horizontal position on said support, the walls of said oven defining a circular spray chamber and a bottom opening and a side port into said chamber and having radially mounted in the circular side wall of said 8 chamber and at the level of said port a plurality of heaters, a support mechanism mounted on said horizontal support below said oven and including a turntable for articles to be spray coated and means for lifting the turntable from a loading position level with the surface of the support up to the oven to close the bottom opening of the oven and for returning the turntable to its original position and including also means for rotating the turntable in a lifted position only, a spray mechanism mounted on said support and including a spray nozzle and means to move the nozzle into and out of the side port of said oven from a position outside said oven, and timing means for said support mechanism and said spray mechanism to effect spray coating of hot articles in said chamber.

7. A spray coating apparatus comprising in combination, a horizontal support, a shallow oven mounted in an elevated horizontal position on said support, the walls of said oven defining a circular spray chamber and a bottom opening and a side port into said chamber and having radially mounted in the circular side wall of said chamber and at the level of said port a plurality of heaters, a support mechanism mounted on said horizontal support below said oven and including a turntable for articles to be spray coated and means for lifting the turntable from a loading position level with the surface of the support up to the oven to close the bottom opening of the oven and for returning the turntable to its original position and including also means for rotating the turntable in a lifted position only, said turntable having a crowned upper centering surface for accommodating article supporting pallets having concave bottom surfaces, a spray mechanism mounted on said support and including a spray nozzle and means to move the nozzle into and out of the side port of said oven from a position outside said oven, and timing means for said support mechanism and said spray mechanism to effect spray coating of hot articles in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,347,994 Day July 27, 1920 2,141,630 Westin Dec. 27, 1938 2,516,908 Pottle Aug. 1, 1950 2,553,191 Hettinger May 15, 1951 

